Prior art digital printing apparatus using liquid toner typically comprise an image forming unit with an imaging member adapted to sustain a pattern of electric charge forming a latent image on its surface, a development member arranged to receive liquid toner, and to develop said latent image by transferring a portion of said liquid toner onto the imaging member in accordance with said pattern. The liquid toner is then applied from the imaging member on the substrate, optionally via an intermediate member.
It is known to apply coatings on printed toner images to reduce the sensitivity to rubbing and/or to improve the gloss. However, such embodiments have the disadvantage that a separate coating unit is needed resulting in an increase of the cost of the printing process.
EP 0 455 343 discloses a liquid toner comprising a curable carrier liquid. It is claimed that by curing the curable carrier liquid after printing the adhesion of the image to the substrate is improved, since the carrier liquid can penetrate in the substrate, and curing results in the image being tightly bound to the fibres of the substrate. Such an embodiment may work for porous substrates, where a surface layer of the carrier liquid is exposed using UV light.